The present invention relates to the production of concentrated aqueous solutions of organic salts of alkylpropylenediamines, more precisely of acetates of N-coco-, N-oleyl- or of N-tallow-1,3-diaminopropanes.
Solutions of this type are used as stock solutions for the preparation of lubricating solutions intended to facilitate the contact sliding between solid surfaces such as glass, metals, polymers (polyethylene terephthalates, for example). In particular, these are solutions of the type which are used to ensure the lubrication of bottles on conveyor lines during bottling, cleaning, filling and labelling operations. For these operations, fatty acid soaps, which are too sensitive to multivalent ions and to which it was necessary to add complexing agents, phosphates and EDTA, which at the same time are costly and ecologically not very recommendable and which, in addition, have a strong tendency to promote bacterial proliferation, have been abandoned. Recognition has now been made (EP-B-0372628) for this use of the advantage of salts of fatty alkylamines, and more particularly those of fatty alkylpropylenediamines (N-alkyl-1,3-diaminepropanes), which relatively are not very sensitive to the multivalent anions present in industrial water, giving solutions without great turbidity, of good lubricating power and exhibiting excellent antimicrobial properties. These products are supplied in the form of formulations with an essentially aqueous solvent, of which a typical composition (EP-B-0372628, Example 1A) is:
These are relatively not very concentrated compositions, which have the disadvantage of occupying large storage capacities in the factories close to conveyor lines. The stock solutions, when their concentration of fatty amines becomes significant, in practice when it reaches and exceeds 30%, have certain disadvantages: they become pasty and difficult to handle and above all, they are very difficult to dilute, as a result of the formation, in the course of dilution, of gelatinous lumps which only redissolve very slowly, and considerably reduce the useful concentration of the lubricating amine.
What has just been found, and what is the basis of the present invention, is that it is possible to have available concentrated solutions of acetates of N-coco-, N-oleyl- or N-tallow-1,3-diaminopropanes which do not have these disadvantages and which are formed of solutions of acetates of this type in a water/dissolving agent solvent. These solutions are characterized in that
their diamine acetate content is greater than or equal to 35% by weight,
the weight ratio of the diamine acetate to the dissolving agent is less than or equal to 4,
the dissolving agent is taken from the group formed by isopropanol, ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, di(ethylene glycol), di(ethylene glycol)monobutyl ether and 4-hydroxy-4-methyl-2-pentanone (or diacetone alcohol),
provided that these formulations pass the 100 second dilution test.
This last condition merits some explanation. What the inventors are teaching is that, against every expectation, the formulations thus defined in composition have the desired characteristics of liquidity, clarity and generally do not suffer from dilution troubles. However, because the commercial products are based on diamines whose statistical distribution of the fatty chain lengths and of the level of unsaturation is fluctuating, and since the phase diagrams of the formulations according to the invention can have anomalies for certain composition variants, a selection is to be carried out to eliminate the imperfect formulae. The test for this is the dilution test, which is of extreme simplicity. In particular, the test will respond differently with the N-cocodiamines, the N-oleyldiamines and the tallow diamines, accepting for the latter only compositions formulated with diamine acetate/dissolving agent ratios of appreciably less than 4, or with certain solvents only from the proposed list.
The solutions used for the treatment of bottles (bottling, cleaning, filling, labelling) in the course of their handling on the conveyor lines are generally aqueous dilutions of the compositions according to the invention having an N-alkylpropylenediamine acetate content varying from 0.001 to 1% by weight, and preferably from 0.01 to 0.1% by weight.